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STANAG 5066: PROFILE FOR MARITIME HF DATA COMMUNICATION
V1.0.2
Annex B: Channel Access Sublayer
(mandatory)
The functions required of the channel access sublayer are quite limited in the ship-shore
application.
B.1 Channel Access Sublayer Service Definition
The Channel Access Sublayer provides services to the Subnetwork Interface Sublayer. These
services are:
1. Execute Physical Link “Make and Break” requests.
2. Notify changes in the state of the Physical Link.
3. Accept S_PDUs (in the appropriate primitive) for transmission.
4. Deliver received S_PDUs (in the appropriate primitive).
In order to provide these services, the Channel Access Sublayer implements a protocol which
specifies the tasks that must be executed and the rules that must be obeyed by the sublayer.
While a number of different channel access protocols are possible, the one that is suitable for
this document is referred to as the type 1 protocol.
B.2 Channel Access Protocol Type 1 and C_PDUs
The Type 1 Channel Access Protocol supports the following subnetwork configuration:
1. Pairs of Nodes are linked “point-to-point” on a “common” HF frequency channel or on
dedicated frequency channels selected from a pool of assigned frequencies by an external
process 5 which is not under the control of any of the sublayers (an ALE sublayer is not
present or not used).
2. The co-ordination of the making and breaking of Physical Links between two nodes
(after a common frequency has already been selected by an external process) is
performed solely by the Channel Access Sublayer.
3. The Nodes may or may not be within ground-wave distances.
B.2.1
Type 1 Channel Access Sublayer Peer-to-Peer Communication
The type 1 Channel Access Sublayer communicates with peer sublayers in other nodes in
order to:
1. Make and break physical links
2. Exchange S_PDUs submitted by the Subnetwork Interface Sublayer.
5 An appropriate frequency may be simply selected manually by an operator or by an external
(semi)automated process e.g. “available” frequencies are negotiated between a node which needs to
establish a link and a master station which “manages” the assigned frequency pool. Protocol type 1
provides no mechanism for automatic interaction between the external process and the Channel Access
Sublayer. The Channel Access Sublayer “assumes” that a common frequency channel has already been
found.
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